A fuel cell is an electrochemical device in which the chemical energy of a conventional fuel is converted directly and efficiently into low voltage electrical energy. Fuel cells have many potential applications such as supplying power for transportation vehicles, replacing steam turbines and remote power supply applications.
Fuel cells, like conventional batteries, operate by utilizing electrochemical reactions. Unlike a battery, in which chemical energy is stored within the cell, fuel cells generally are supplied with reactants from outside the cell. Barring failure of the electrodes, as long as the fuel (preferably hydrogen), and the oxidant (preferably either oxygen or air that contains oxygen) are supplied and the reaction products are removed, the cell continues to operate.
Fuel cells also offer a number of important advantages over engine or generator systems. They include relatively highly efficient, environmentally clean operation especially when utilizing hydrogen as a fuel, high reliability, few moving parts, and quiet operation.
A schematic diagram of a fuel cell with the reactant/product gases and the ion conduction flow directions through the cell is shown in FIG. 4. Referring to FIG. 4, the major components of a typical fuel cell 10 is an anode 14, a cathode 16 and an electrolyte layer 12. In the embodiment shown, the anode 14 and the cathode 16 are each in contact with and positioned on opposite sides of the electrolyte layer. During operation, a continuous flow of fuel, commonly hydrogen, is fed to the anode 14 while, simultaneously, a continuous flow of oxidant, commonly oxygen or air, is fed to the cathode 16. In the example shown, the hydrogen is fed to the anode 14 via a hydrogen compartment 13. Likewise, the oxygen or air is fed to the cathode 16 via an oxygen/air compartment 17. The fuel is oxidized at the anode with a release of electrons through the agency of a catalyst. These electrons are conducted from the anode 14 through wires external to the cell, through the load 18, to the cathode 16 where the oxidant is reduced and the electrons are consumed, again through the agency of a catalyst. The constant flow of electrons from the anode 14 to the cathode 16 constitutes an electrical current that can be made to do useful work. Typically, the reactants such as hydrogen and oxygen, are respectively fed through the porous anode 14 and cathode 16 and brought into surface contact with the electrolyte 12. The particular materials utilized for the anode 14 and cathode 16 are important since they must act as efficient catalysts for the reactions to take place.
Despite their potential advantages, fuel cells have not been widely utilized due in large part to their relatively high cost. An important factor contributing to this high cost is the catalytic inefficiencies of the prior art catalytic materials and/or the high costs of many of these materials. The catalytic inefficiencies of the materials increase the operating costs of the fuel cell since such inefficiencies result in a lower electrical energy output for a given amount of fuel. The use of expensive catalytic materials, such as noble metal catalysts, results in fuel cells which are too expensive for widespread application.
High catalytic efficiency at low cost is a desired result which must be attained before widespread commercial utilization of fuel cells is possible. Prior art fuel cell anode catalysts, which have been generally predicated on either expensive noble metal catalysts with a relatively low density of catalytically active sites, have not been able to meet the requirements. The present invention is directed toward novel, low cost and highly efficient catalytic materials that are useful for a variety of applications such as a fuel cell anode. The present invention is also directed toward an efficient and inexpensive method of making the novel catalytic materials.